2004 350Z , Slip light when not slipping (or is it?)

[PalmerWMD]

I have the following problem.

Sometimes when accelerating hard my slip light comes on, before everbody goes "lol,go figure", let me explain that the tires arent slipping.

At all.

This happesn during totally dry roads and good traction and i dont feel any slip at all ( been monitoruing that very closely and I know what slipping even suightly slipping tires feel like)

This problem has been around, even before my SC went on.

Seems to occur between low3k's and low4's.

Sometimes just the slip light comes on and then nothing ( ie no throttle retard)And sometimes the TCS does take out throttle ( always noticable).

At one time i was wondering if my aftermarket tires are confusing the TCS, but they are the <exact> size and stagger of the stock Track wheels ( mine is an enthusiast stocks are 17's), Also they are the exact size of the G35C sports edition tires (as this is where the wheels come from.)

So while not stock on a Z33 enthusiast, this size is stock on Z33 touring, Z33 Track and G35C 6 Speed in 04 and I would expect the TCS to be calibrated the same on all of these as on mine.

Any ideas?

Fred..

[Netko350Z]

Sometimes happens with mine as well. What size tires are you running?

[PalmerWMD]

225/45-18 in front on G35C 18x8 wheels (Edited for accuracy)245/45-18 in rear on G35C 18x8 wheels.

Exact dimenions of Track/Touring

Fred..

PS: Dont forget to check out our Nico 350Z forum:zeroforum?id=168

[NISTECH]

Fred I have seen it on a couple Z's I have driven and have found that the tires and wheels on those were aftermarket. I had a customer concern 1 time for the same thing but found he had a 3 psi diference between 2 of the tires. By setting all the tires dead on 35 psi problem was resolved[he had factory wheels and tires though] Now on the cars I noticed it on I dont know what was causing it as the customer did not express a concern over it so we dont mess with it if the customer doent mention it. It was on hard accel with out breaking the tires loose. All I can say fred is check your tires pressures and make sure they are dead on 35 psi. If this does not fix it then my only recommendation would be to through a set of stocks[for your car] back on and see if problem still exists. I do know these systems are very sensative, and also know your cars speed you see on the speedometer is taken from the ABS wheel sensors via the ABS module. There is no speed sensor in the trans any more.

[PalmerWMD]

My rears are exactly at 35psi and my fronts at 38 psi. (so you think i should?)

But I'll go out right now and double check.

I dont want to lower the front psi if I can help it.

Like I said tire sizes (ie wheels diameter) match stock at least according to specs.

I had the problem before with the stock wheels and my winter tires as well ( tires sizes excatly as stock)..

So tire diamters should be same..

Of course there are production variances between tire makers, so I could be off I guess..

but the tire diameters between 17's stock and 18's stock are slightly different too, So I figured the TCS wouldnt be too sensitive?

So you feel its the TCS being too sensitive, perhaps brought on by tire diameter very slightly deviant from stock (number are same so would have to be very sliight diff)?

Fred..

[NISTECH]

No I missed the part where you mentioned it did it on stock. Honestly I dont feel it has to do with actual tire size as it looks for difference in speed of one tire from another when it throws on the slip light and does throttle cut. The tire pressure difference could be your problem at least try to drop them down to factory specs and see if it resolves your problem.

[PalmerWMD]

Just double checked my psi they are all spot-on.

I like to keep my fronts at 38 due to lower load rating of tire and more weight up front, rears 35 is plenty i feel, since load rating is 103 on these tires, and its onlya 3200 lbs car...

Fred..

[s13sr20chris]

i have had one issue with the abs sensors not sitting very well in the diff cover. it caused the same issue you are having as well as occasional abs action on non-sliding stops.

will it happen on a flat road going straight?

[PalmerWMD]

No I missed the part where you mentioned it did it on stock. Honestly I dont feel it has to do with actual tire size as it looks for difference in speed of one tire from another when it throws on the slip light and does throttle cut. The tire pressure difference could be your problem at least try to drop them down to factory specs and see if it resolves your problem.

It did it on stcok wheels but they werent stock tires ( Michelins in as stock size)

I swear when this happens there is no slippage at all I can feel andi am very sensitive to those things..But nothing to do with a possibly slipping clutch, as no speed sensors in transmission? right?

Fred..

[PalmerWMD]

i have had one issue with the abs sensors not sitting very well in the diff cover. it caused the same issue you are having as well as occasional abs action on non-sliding stops.

will it happen on a flat road going straight?

When I noticed it first it happend on a downhill entry ramp and was even repeatble (stock wheels winter michelins in stock size) no slip at all.

Its not super common, but happens maybe once a week and usually at hi throttle but not real hi revs at all.

So far I noticed it when going straight or very nearly going straight.

Fred..

[s13sr20chris]

i wonder how much the extra pressure in the fronts changes your actual tire circumfrence. if you stack that with the track model stagger on an enthusiast model(if the tcs is programmed different as i assume it is) it may make the car that much more sensitive to variations in wheel speed front to back. think also, if you are accelerating you are compressing the rear susp/tires and unloading the fronts. i know in extreme cases this causes the front tires to "grow" and the rears to "shrink". the extreme case i know of was of a certain ruf btr on the autobahn going close to 200mph but with speedo reading only 190+. this is due to 911 speedos being driven off of the left front wheel. of course in that case the front end lift was aerodynamic rather than torque reaction. does that matter? i dunno.

[PalmerWMD]

Chris those are good considerations and I went thru them in my head as well.however I pose those effects will lessen the speed differential, the TCS sees, between pairs, as the front are smaller, than the rears.

All350Z of course are like that, but in the G35C/350ZTrack sizes ,this difference is more pronounced.

So the effect you describe, would bring wheel diameter/tire revolutions more in line with the 17 inch stock set-up, ie. lessen the difference from front to rear tire revolution, since 17 has less of a stagger/differential in tire revolutions between front and back.

Fred..

[NISTECH]

It did it on stcok wheels but they werent stock tires ( Michelins in as stock size)

I swear when this happens there is no slippage at all I can feel andi am very sensitive to those things..But nothing to do with a possibly slipping clutch, as no speed sensors in transmission? right?

Fred..

no slipping clutch It doesnt look at that, it makes the decision to cut throttle when it slips based on each ABS wheel sensor speed input to the ABS control module. The only difference between a stock abs control car and yours is software in the module, the only diffenrnce on the VDC is the software and 2 additional sensors [lateral G-force sensor and Yaw rate sensor.]

[PalmerWMD]

So there <is> a difference in TCS software, from Enthusiast to track Models?

that <would> explain it

Fred..

[NISTECH]

No not from modle to model but from ABS-TCS -and VDC. It depends on the option in the car. Now yes There probably is a difference in the software if the tires are different sizes between the 2 models.

[PalmerWMD]

all the VDC equipped cars from with 18 inch.. So maybe tehre is a difference.So I would pose an enthusiast with the Nismo wheels, with even bigger stagger, should experience this same phenomenon if we surmise correctly..

(Sorry I dont ask often in here, but when I do, its hard ones)

Fred..

[NISTECH]

As I said its not based on tire size but on speed indifference between tires. In a turn you might have a bigger difference on larger or smaller tires, but as you say your going straight so there should be no exagurated[sp?] difference even if you did have bigger tires. The sensors in the wheels work on the same basic principle as the old styl speed sensors. It is mearly a on of signal generating a pulse to the ABS control unit. If the tires were bigger the signal would just be slower if they were smaller it would be faster. How ever there is a clibrated difference for the staggered set up. If you were to take 2 larger tires and put them on the difference would simply step down but be with in the same range of calibration. If you were to go from non stagered to staggerd you would have a problem.... make sence?

[PalmerWMD]

I went from stock Enthusiast 225/50-17--235/5--17 to 225/45-18--245/45-18

So.. the TCS on an Enthusist, expects to see the 17 (lesser) stagger and the TCS on a Track expects to see the stagger of the Track sizes?

[NISTECH]

I might be wrong but arent those both the same overall diameter due to the lower profile on the larger diameter rims?

[PalmerWMD]

They are close ut there is a difference , also the stagger is different from Enthusiast/Base to Track/touring with the latter having a more pronounced stagger..

[PalmerWMD]

Awesome tool to compare:http://www.miata.net/garage/tirecalc.html

Track/touring/'04 G35C-6Speed:225/45-18 in front on G35C 18x8 wheels (Edited for accuracy)245/45-18 in rear on G35C 18x8 wheels.

Base/Enth:225/50-17235/50-17

Fred..

[NISTECH]

Here is some coparision info.

[NISTECH]

There is no listed difference in the service manual or owners manual about the different model levels only tire options.

[NISTECH]

Here is your tread and deminsion info on both cars